Algal cells are a promising source of biofuels (Wijffels & Barbosa (2010) Science 329:796-99). Their ability to harness solar energy to convert carbon dioxide into carbon-rich lipids already exceeds the abilities of oil-producing agricultural crops, with the added advantage that algae grown for biofuel do not compete with oil-producing crops for agricultural land (Wijffels & Barbosa, 2010). Tetraselmis phytoplankton are unicellular marine green algae that can be cultured easily, rapidly, and economically. In order to maximize algal fuel production, new algal strains will need to be engineered for growth and carbon fixation at an industrial scale (Wijffels & Barbosa, 2010).
Modern recombinant strain development requires robust and efficient tools for expressing transgenes to alter cellular metabolism and physiology in desired ways. An essential component of any “toolkit” is a suite of functional promoter elements to drive transgene-expression. As such, there is a need for endogenous promoters, cloned and verified, from the strains for which recombinant DNA technology is being developed. There is a comparative lack of knowledge relating to techniques suitable for transforming Tetraselmis cells with transgenes, particularly of constitutive promoters and terminators derived from Tetraselmis species.
Transformation of Tetraselmis subcordiformis by glass bead treatment of protoplasts has been reported. See Cui et al. (2010) World J. Microbiol. Biotechnol. 26:1653-57. However, this method demonstrated only transient detection of the transformed gene—a green fluorescent protein controlled by a cytomegalovirus promoter—and did not make use of a selectable marker.
Further, while it will be necessary to manipulate the Tetraselmis genome in order to maximize biofuel output, this has proven difficult to date because of the thick cell wall that surrounds Tetraselmis cells. Better procedures for genetic manipulation of these organisms are urgently needed.